Could you please clarify your question? Are you trying to add a font named Cyr, trying to add a font that supports cyrillic characters, or something else?
Trying to add a font named Cyr
This is not something currently supported but you can add or vote on feature ideas: http://forums.adobe.com/community/formscentral?view=idea
If you need to add a new idea click "Create an idea" under "Actions" in the top right.